The present invention relates to apparatus for inserting an intraocular lens through a small incision into an eye, to methods for making such apparatus and to methods for inserting an intraocular lens into an eye. More particularly, the present apparatus has enhanced lubricity and stability, can be relatively easily and effectively manufactured, and is useful for inserting a foldable intraocular lens into an eye.
An intraocular lens (IOL) is implanted in the eye, for example, as a replacement for the natural crystalline lens after cataract surgery or to alter the optical properties of (provide vision correction to) an eye in which the natural lens remains. IOLs often include an optic, and preferably at least one flexible fixation member or haptic which extends from the optic and becomes affixed in the eye to secure the lens in position. The optic normally includes an optically clear lens. Implantation of such IOLs into the eye involves making an incision in the eye. It is advantageous, to reduce trauma and speed healing, to have an incision size as small as possible.
IOLs are known which are foldable (deformable) so that the IOL can be inserted through a smaller incision into the eye. A substantial number of instruments have been proposed to aid in inserting such a foldable lens in the eye.
Many of the prior art IOL insertion systems load and/or fold the lens at the distal end, that is, at the end inserted into, or closest to, the eye. Such “distal loading” systems often disadvantageously include a space consuming loading component at or near the distal end of the system which causes the distal end to be relatively large. This relatively large distal end makes inserting the IOL through a small incision more difficult, if not impossible. Systems which fold and load the IOL proximally of the distal end provide certain advantages, such as reduced stress on the IOL and/or inserter, relative to “distal loading” systems.
However, whether using a distal loading or proximal loading system, one factor which has historically determined the minimum diameter of the inserter tube involves the inserter tube itself. For example, the material from which the inserter tube is made, such as polypropylene and the like polymeric materials, may have a relatively high coefficient of friction, causing it to provide a relatively high amount of resistance to an optic made, for instance, from silicone polymeric materials, as it passes through the tube. The amount of resistance, and thus the amount of force (torque) required to pass an IOL through the tube, increases as the diameter of the tube decreases. Since increased torque on the IOL increases the potential for damage to the IOL and/or the inserter tube, as well as injury to the patient, it is desirable to keep the required torque as low as possible.
One way to reduce the amount of force needed to pass an IOL through a small diameter insertion tube is to provide a lubricity enhancing component, such as a coating, on the exposed interior surfaces of the inserter. Examples of IOL inserters having an interior wall coated or otherwise provided with a lubricity enhancing component include Makker et al. U.S. Pat. No. 5,716,364 and Yang et al. U.S. Pat. No. 5,803,925. The disclosures of each of these patents are incorporated in their entireties herein by reference.
The aforementioned Makker patent discloses a method of making an inserter that comprises compounding a hydrophilic lubricity enhancing component such as glycerol monostearate (GMS) into the polypropylene resin used to fabricate the inserter. The interior wall is preferably then exposed to plasma and subsequently subjected to elevated temperatures for a sufficiently long time to cause the lubricity enhancing component to bloom to the surface of the cartridge. After blooming, the lubricity enhancing component functions as a low-friction coating that is non-covalently bonded to the interior wall of the inserter.
The Yang et al. patent discloses an inserter having a lubricity enhancing component covalently bonded to an interior wall. An exemplary lubricity enhancing component disclosed in Yang et al. comprises a compound having the formula A-PEG, where A is a reactive group capable of covalently bonding to the surfaces of a polypropylene IOL inserter, and PEG is a residue of polyethylene glycol.
While many of the prior art lubricity enhancing components are generally satisfactory, further improvements are desirable. For instance, in inserters having non-covalently bonded GMS-based lubricity enhancing components such as those disclosed in the aforementioned Makker et al. patent, the blooming process may continue even after exposure of the inserter interior wall to high temperatures has stopped, which can eventually result in excessive amounts of GMS on the surface of interior wall. Such inserters have the potential of causing excess GMS to be transferred onto the surface of an IOL optic during insertion, causing unsightly blemishes or streaks on the optic. The shelf life of these prior art GMS-based cartridges is limited to one year, for example, to avoid this potential risk. On the other hand, prior art cartridges having covalently bonded lubricity enhancing components may involve more complex manufacturing processes, require higher torque to pass the IOL through the tube, or may be at potential risk of reduced stability, for example, because of hydrolysis of the coating, over time. Such prior art cartridges also have limited shelf life to avoid this potential stability risk. Likewise, a simplified mode of generating an appropriate matrix for cross-linking of involved substituents for example a dialdehyde and a polymeric amine prior to dispersal and/or avoidance of extended times associated with plasma treatment serves to enhance industrial efficiency and is progress in science as a useful art.
Accordingly, it would be advantageous to provide stable, long-lasting lubricity-enhancing coatings for IOL insertion apparatus which facilitate the passage of folded IOLs through the apparatus in a controlled manner without using excessive force. It would also be advantageous to devise cost-effective and simple methods of making and using insertion apparatus.